Therefore, alternative interventions with the potential to improve hamstring extensibility remain of interest. As an alternative intervention, recent randomised studies have examined the application of vibration to the whole body in healthy or athletic participants. Whole body vibration significantly improved the results of simple clinical tests such Epigenetics Compound Library as the sit-and-reach test (Fagnani et al 2006, Sands et al 2008, Jacobs and Burns 2009), although clinically the effects

would be considered small to moderate. Issurin (2005) has suggested that whole body vibration may enhance excitatory inflow from muscle spindles to the alpha motorneuron pools and modulate the recruitment thresholds and firing rates of motor units and also depress the inhibitory impact of Golgi tendon organs providing more flexibility. An alternate hypothesis is that the improved flexibility performance may be due to the increased neural potentiation of the stretch reflex loop induced by vibration (Cochrane and Stannard, 2005). Notably, these randomised studies used a whole-body intervention and range-of-motion tests that involve multiple muscles. Localising the application of the intervention and the measurement of the effect may help to clarify

the effect. Also, local application of vibration is simpler, cheaper, Ibrutinib and more widely available. However, studies that have examined more localised application of vibration have applied it to multiple over local sites, have not used a range of motion test localised to a single muscle, and/or lacked an appropriate control group (Atha and Wheatley 1976, Issurin et al 1994, Kinser et al 2008, Cronin et al 2008). The results of these studies are inconsistent. Because of these issues, the effect of local vibration on hamstring extensibility is still unclear. In the absence of the equipment to test muscle extensibility directly using standardisation of torque with recording of electromyography, we elected to examine the effect of local vibration over the hamstrings on the range achieved on the passive knee extension test (Kendall et al 2005, Gnat et al 2010). Given the gender differences

noted above, we restricted the participants to one gender. Therefore the study question was: Does local vibration over the hamstrings improve the range of knee extension achieved on the passive knee extension test in healthy women? A randomised trial with concealed allocation, intention-to-treat analysis, and assessor blinding was conducted. Participants were recruited from students at Semnan University of Medical Sciences, Iran. An individual interview was carried out to collect demographic and physical assessment data. After their eligibility was confirmed, participants were randomly allocated to one of two groups. Randomisation was achieved using a computer-generated random list drawn up by the statistician. The list had a block size of 30 but was provided to the recruiting investigators in sealed opaque envelopes.